Diagnosing Noise Issues - TDT Medusa4Z User Manual

subject and no stimulus presentation. The easiest way to achieve this is to simply disconnect
the speaker. When running this test, the noise floor will typically go up by 20%. If the noise floor
increases by more than 20% the problem is likely subject related (sedatives, etc).

Diagnosing Noise Issues

Electrical noise is one of the most common problems users must address. Luckily, most
problems can be resolved easily.
Here are a few common sources of noise:
The charger for the Medusa4Z was left plugged in
Always disconnect the preamplifier from the charger and rely on the battery during recordings. No high voltage
lines should be used inside the Faraday cage. Also disconnect the charger from the wall.
Note
Some subject enclosures may include interior lights or fans. These should not be used or connected to
power during ABR recordings.
Ground and reference are placed incorrectly
See Electrode Placement
Electrode impedances do not match
Channel 1 and Reference impedances should match at 1K-3K each.
Something near the recording area is causing noise?
The nearby area should be as free of high voltage noise sources as possible. Common sources are motors, fans,
refrigerators, freezers, lights, and computer monitors.
The subject enclosure does not have a dedicated ground
If your noise floor is higher than expected, we recommend tying the cage to a dedicated ground or connecting it to
a nearby copper pipe, if possible. Use caution if you use an electrical outlet ground. These are commonly tied to
other outlets that could introduce noise.
for correct placement.
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